"What they were doing in the 1960s came out of an innocence that we've lost. No one knew things weren't possible then; everybody could be absolutely themselves, and Oz magazine was about that generation's right to speak freely."

Next up, Sienna is set to star in A Woman of No Importance, a comedy co-starring Annette Bening.

The 25-year-old, who has been keeping close company with Rhys Ifans in recent months, is planning to eventually step away from the spotlight, albeit briefly.